The move is in response to Donald Trump's presidential victory last week. The president-elect won through the Electoral College, although Hillary Clinton is leading the popular vote by nearly a million votes, a statement from Boxer's office read.

Trump won the presidency by securing at least 290 electoral votes while Hillary Clinton recieved 228, with two states still left to call, according to NBC News. Boxer was a Clinton supporter.

"When all the ballots are counted, Hillary Clinton will have won the popular vote by a margin that could exceed two million votes, and she is on track to have received more votes than any other presidential candidate in history except Barack Obama," Boxer said.

Trump will be the fifth president in U.S. history to win the election despite losing the popular vote. George W. Bush won the most recent such election, in 2000.

"This is the only office in the land where you can get more votes and still lose the presidency," Boxer said in a statement. "The Electoral College is an outdated, undemocratic system that does not reflect our modern society, and it needs to change immediately. Every American should be guaranteed that their vote counts."

Four years ago, Trump called the Electoral College "a disaster for a democracy," in a tweet sent on Nov. 6, 2012.

If Boxer's amendment were to pass, it would amend the U.S. Constitution, and "would take effect when ratified by three-fourths of states within seven years after its passage in the U.S. Congress," the statement from Boxer's office read.

The bill is not expected to advance in the GOP-controlled House and Senate.